tekmar 275 Boiler Control - Manual (Page 7)

7 of 48 © 2012 275_D - 11/12
Stage Delay Setting in Adjust Menu
The Stage Delay is the minimum time delay between the
firing of each stage. After this delay has expired the control
can fire the next stage if it is required. This setting can be
adjusted manually or set to an automatic setting. When the
automatic setting is used, the control determines the best
stage delay based on the operation of the system.
Boiler Relay Setting in Adjust Menu (per boiler)
The 275 provides a dry contact for either burner ignition or
boiler pump. Selection is made through the Boiler RELAY
setting in the adjust menu. Select ‘burner’ for boilers that
require a boiler enable signal as well as a modulating signal
in order to operate. Select pump to operate a boiler pump
with post purge capabilities.
Boiler Mass Setting in Adjust Menu (per boiler)
Match the boiler mass setting with the thermal mass
characteristics of each boiler. The modulation of the boiler
can become unstable if the incorrect Boiler Mass setting is
chosen. A key sign of unstable boiler modulation is that the
flame will continue to increase and then decrease in short
periods of time. By choosing a lower boiler mass setting,
the boiler response will become more stable.
LO
The LO setting is selected if the boiler that is used has
a low thermal mass. This means that the boiler has very
small water content and has very little metal in the heat
exchanger. A boiler that has a low thermal mass comes
up to temperature quite rapidly when fired. This is typical
of many copper fin-tube boilers.
The Lo mass setting provides a fast response to the heating
system.
MED
The MED setting is selected if the boiler that is used has
a medium thermal mass. This means that the boiler either
has a large water content and a low metal content or a
low water content and a high metal content. This is typical
of many modern residential cast iron boilers or steel tube
boilers.
The Med mass setting provides a moderate response to
the heating system.
HI
The HI setting is selected if the boiler that is used has a
high thermal mass. This means that the boiler has both
large water content and a large metal content. A boiler that
has a high thermal mass is relatively slow in coming up to
temperature. This is typical of many commercial cast iron
and steel tube boilers.
The Hi mass setting provides a slow response to the
heating system.
Boiler Differential Setting in Adjust Menu
A modulating boiler must be operated with a differential
while operating at Minimum Modulation. When the boiler
is modulating above Minimum Modulation, the differential
does not apply. Instead, the modulation output signal is
determined using Proportional, Integral, and Derivative (PID)
logic in order to satisfy the boiler target temperature.
The boiler differential can be fixed or automatically
determined by the control. The Auto Differential setting
balances the amount of temperature swing in the boiler
supply temperature with boiler on times, off times, and
cycle times. This reduces potential short cycling during
light load conditions.
Manual Differential
Differential = 10°F (6°C)
Target + 1/2 Differential
Target – 1/2 Differential
Target
165°F (74°C)
160°F (71°C)
155°F (68°C)
Boiler
On
Boiler
On
Automatic Differential
Off
Differential
Time
Heating Load
On
Rotation
The Rotate feature changes the firing order of the boilers
whenever one boiler accumulates 48 hours more run time
than any other boiler. Rotation will be forced if any boiler
accumulates 60 hours more run time. After each rotation,
the boiler with the least running hours is the first to fire and
the boiler with the most running hours is the last to fire.
This function ensures that all of the boilers receive equal
amounts of use. When the Rotate / Off DIP switch is set
to the Off position, the firing sequence always begins with
lowest boiler to the highest boiler.
720 hours
1 2
672 hours 720 hours
2 1
672 hours
To reset the rotation sequence (without regard to historical
running hours), toggle the Rotation DIP Switch Off for 3
seconds and on again. Note that the running hours (see
Run Time) in the View menu also need to be reset if you
want the rotation sequence and running hours display to
be synchronized.
Boiler Run Time in View Menu
The running time of each boiler is logged in the view menu.
To reset the running time, select the appropriate Boiler Run
Time in the View menu and press and hold the Up and
Down buttons together until CLR is displayed.